1. Field of the Invention
This invention generally relates to methods of ink printing and, more particularly, to multicolor ink printing on textiles. This invention also relates to systems and apparatus for multicolor ink jet printing on textiles, as well as multicolor ink printed textiles, per se.
2. Description of the Prior Art
As defined herein, the term xe2x80x9ccolor spacexe2x80x9d is a mathematical definition for colors. Well known color spaces include CIE lab, CIE xyz, CIE luv, CIE xyY, CIE uvY, Cyan-Magenta-Yellow-Black (CMYK), and Red-Green-Blue (RGB). For example, the RGB triplet divides each color into an amount of red, green, and blue, such as (50,40,220) for a blue dominant color.
The simple act of printing a color image on textiles is well-known. In fact, the history of dying cloth may go back as far as 2600 B.C.
Nonetheless, numerous technical difficulties remain in attempting to accurately print an image or design on a textile. For example, refraction and internal reflection caused by the chosen textile results in color interference, which is perceived as a muddy or blurry image. Moreover, each textile fabric has a different set of refraction and internal reflection characteristics, and different weights and weaves of the same fabric will have different sets of refraction and internal reflection characteristics. The high level of variation of refraction and internal reflection often necessitates custom preparation of color separations for each type of fabric in order to avoid color interference. Yet, custom preparation of color separations takes a great deal of time and effort on the part of the textile colorist. Of course, the technical difficulties of printing multicolor images on textiles increases as the image or design becomes more complex.
Overall changes in the printing and imaging industries compound the traditional problems, especially as digital technology becomes the norm rather than the exception. For example, digital images are routinely coded in RGB for display on a computer monitor. However, printers typically use CMYK and textile colorists traditionally use CIE lab. Thus, an image initially in RGB will be routinely converted into a different color space before being printed. However, data can easily be lost or corrupted in the conversion to a different color space. Software correction may be applied in an attempt to recover lost or corrupted data, but such software correction may actually increase the errors.
Many prior art methods for non-textile printing attempt to overcome the disadvantages inherent in multiple color space transformations, such as U.S. Pat. Nos. 5,450,217 to Eschbach et al. and 5,953,499 to Narendranath et al. These patents rely on artificial blending or filtering color space data to xe2x80x9cenhancexe2x80x9d or xe2x80x9cimprovexe2x80x9d the subsequently rendered image. Yet, clearly, such forced techniques are not ideal.
Printed images on textiles can be blurry because the colors bleed into or blend with one another. Color correction is often accomplished using gray replacement with undercolor addition or using undercolor removal. However, as stated above, it is preferable to achieve appropriate color separation without resorting to color correction. Bleeding and blurriness may also be reduced by manipulating the size of the individual ink dots deposited on the textile. U.S. Pat. Nos. 6,051,036 to Kusaki et al. and 6,142,619 to Miura et al. disclose recent attempts to increase printing accuracy by adjusting the size of the ink dots deposited on the textile. Yet, while overall sharpness may be enhanced, subtle blending and shading risk being attenuated, which would detrimentally affect the fidelity of the printed image or design.
Improvements in hardware and software make it possible to use more than three dyes to make a color. Current systems and method usually do not utilize current technology to its full potential. Currently, gray scales are usually made with a dithered black, a dithered gray, or a combination of both dithered black and gray. Yet, dithered blacks and grays generally do not reproduce deep and true blacks and grays. It has been found that, using multiple overlapping sets of complementary colors, a composite shading scale can be built that provides a robust shading scale without visible dithering patterns and also allows for subtle casts to color renderings.
The aforementioned Kusaki et al. and the Miura et al. patents disclose ink jet printing using a maximum of eight colors. The ink jet printing art is generally directed to printing with sets of 4 to 8 differently colored inks. This direction of the art is further discussed in U.S. Pat. No. 5,833,743 to Elwakil.
It is also a long accepted practice, as underscored in the Kusaki et al. patent that different types of dyes (e.g., acid and fiber-reactive) may not be intermixed for printing on fabrics other than silk. In other words, fiber-reactive dyes are used on cotton, silk, and wool, while acid dyes are used on nylon and silk.
There is a need in the art for a system that provides both a broad range of shading and vivid, bright, and true colors, wherein complex digital images can be faithfully printed on a range of fabrics.
In light of the foregoing, it is an object of the present invention to provide a method for printing an image on a textile directly from a digital image with specific user-defined inks.
It is also an object of the present invention to provide such a method for printing an image on a textile, wherein the user selects 8 to 16 inks to create a user-defined high-multiplicity ink set. The user-defined ink-set is linearized with user-defined calibration curves.
It is a further object of the present invention to provide such a method for printing an image on a textile, wherein the pixels of the digital image are directly correlated with the ink set using hue and shade values, without transformation into conventional color spaces, such as CIE lab, CIE xyz, CIE luv, CIE xyY, CIE uvY, or CMYK.
In addition, it is an object of the present invention to provide a system for selecting inks for printing on a textile, in which a user-defined ink set profile is used to correlate an amount of inks with hue and shade values derived directly from the pixels of a digital image defined in the RGB color space.
Moreover, it is an object of the present invention to provide an apparatus for textile printing having a plurality of inks calibrated as a user-defined ink profile that prints an amount of selected inks on a fabric based on hue and shade values from the pixels of a digital image.
Furthermore, it is an object of the present invention to provide a printed textile having a high dpi (dots per inch) count, and a broad range of color density and shading.
It is a further object of the present invention to provide a printed textile with different types of dyes (e.g., acid and fiber-reactive), and yet achieve faithful reproduction of complex pictorials and images.
These and other objects of the present invention are preferably achieved by a method of reproducing a digital image on a textile including the steps of the user selecting 8 to 16 inks to form an ink set, calibrating the ink set to create an ink set profile, using the ink set profile to calculate hue-based and/or shade-based look-up tables (LUTs) that directly correlate the inks with the color space coordinates (e.g., RGB values) of the pixels of the digital image. By directly correlating the inks and the color space coordinates using hue and shade, the present method faithfully reproduces the digital image on the textile. The method may be practiced using a system and/or apparatus that provides means for performing the calibration of the ink set and direct correlation of the color space coordinates. The printed fabric has a first plurality of dots having 8 to 16 differently colored inks per dot and a second plurality of dots having one color per dot. The 8 to 16 differently colored inks are user-defined and avoid certain conventional art directed ink jet ink-set colors, particularly including gray. Significantly, the method, system, and apparatus produce a printed textile having a high level of detail, depth of color, and broad range of shading. The printed textile also has a combination of dye types that heretofore were considered incompatible. One preferred embodiment has 12 inks, which includes or provides 7 true colors, 4 pseudo-colors (i.e., a mix of two or more true colors), and black, and wherein 8 colors are fiber-reactive inks and 4 colors are acid inks.